Young Muslims are being radicalized "in their bedrooms" through direct contact with Islamic State fighters via the Internet, according to terror experts. There are growing concerns authorities and Internet providers are not doing enough to counter online extremism, which analysts say is spread by a prolific network of online supporters around the world.

Treading carefully across the snow-covered tarmac of a bus station in Istanbul, Turkey, grainy CCTV footage shows three British schoolgirls - two aged 15, one 16 - on their way to join the Islamic State. The video emerged last week after the teenagers were believed to have crossed the border into Syria.

What drove these high-achieving students to leave their families for a war zone - to likely become the partners of Islamic State fighters? Britain’s lead counterterrorism police officer, Peter Fahy, blames social media. “The change we have seen over the last few years is these extremist messages are now pumping through the Internet right into your child's bedroom,” he stated.

Investigators said another British woman, Aqsa Mahmood, who had traveled to the Islamic State in Syria, helped recruit the teens.

It is a phenomenon that is happening with increasing frequency across the world as part of the IS foreign recruitment drive for both male fighters and potential female partners, according to terror expert Shiraz Maher of Kings College London, speaking at the policy institute Chatham House.

“Today, you can have a direct dialogue with a fighter. You can ask them what life is like on the ground. You can ask them how they got there,” said Maher. “And that in many respects helps you overcome your own fears, or whatever it is that is stopping you from going.”

Maher said these online ‘Q and As’ often center on the impact on families back home.

“How did you tell your mother that you came out here to Syria? How did you essentially get over and emotionally reconcile the fact that you are breaking her heart?”

Islamic State propaganda also relies on a network of what Maher terms ‘fanboys’ and fangirls.'

“We call them ‘disseminators.’ And these disseminators are incredibly important insofar as because they are not on the ground,” said Maher. “They are able to aggregate large amounts of information from multiple sources and to spread it.”

One of the most prolific disseminators lived in Bangalore, India, operating under the Twitter name ‘Shami Witness.’ He was arrested in December. The Shami Witness Twitter account, now inactive but still accessible, has more than 17,000 followers and included IS propaganda, advice for would-be recruits and messages praising dead fighters.

U.S. Director of National Intelligence James Clapper said Monday his biggest worry is home grown extremism inspired via the Internet. “ISIL particularly is very slick. Very sophisticated proselytizing and recruiting and they are very astute users of social media. So this is a challenge for us as it is in Europe,” he stated.

Security analysts said extremist propaganda on the web must be countered using the same Internet tools to prevent more young people from turning online curiosity into radicalized reality.